1. Field
The present invention relates to a stress visualization device. More particularly, the invention relates to a device for measuring and visualizing distribution of stress applied to an object or internal stress of an object by an optical method. The invention also relates to a device for visualizing tomographic distribution (cross-sectional distribution) of mechanical property value of an object.
2. Description of Related Art
In recent years, composite materials have rapidly expanded their applications in various fields including aviation and space, automobiles, electronic components, and medical equipment. Such composite materials have diversified in shape and size, and have been miniaturized. Since a composite material has an interface of a base material and a reinforcing material, microscale internal defects such as interfacial peeling and transverse cracks may be intricately interrelated. This leads to fracture of the composite material. There have therefore been demands for development of non-destructive measurement techniques enabling quantitative evaluation of mechanical conditions such as stress concentration inside a material.
A method of measuring residual stress on the surface of an object to be inspected in a non-destructive and non-contact manner by an optical technique is proposed as one of such measurement techniques (refer to JP 2008-134186 A, for example). This technique includes irradiating the surface of an object with laser light for heating and laser light for deformation quantity measurement, obtaining the total deformation between before and after thermal stress relief of an inspection area by optical interferometric measurement, and subtracting a deformation quantity induced by a thermal strain from the total deformation quantity, to calculate a deformation quantity induced by residual stress. The technique further includes dividing the deformation quantity due to the residual stress by the difference in Young's modulus between before and after heating, to calculate the residual stress.